GTP for integration of multiple access

ABSTRACT

A network architecture comprising at least one core network, each core network comprising a number of packet data gateway access supporting nodes GASNs handling mobile user station access over an access network, said core network(s) further providing access to one or more global packet data communication networks (IN), and one or more nodes holding subscriber or mobile user station related information. The GASNs are further adapted to support intercommunication over a mobility protocol interface to, at reception of a request for change of access type from a mobile user station, establish information about the previous GASN of the mobile user station, and to, using the established information, update an established communication context concerning the mobile user station or create a new communication context concerning the mobile user station such that mobility between different access network types is enabled for a mobile user station without interruption of an ongoing session.

FIELD OF THE INVENTION

The present invention relates to a network architecture which comprisesat least one core network. Each core network comprises a number ofpacket data gateway access supporting nodes handling mobile user stationaccess over an access network and which core network also providesaccess to a global packet data communication network or a third partycontrolled packet data network. It further includes a system of one ormore nodes holding subscriber or mobile user station relatedinformation.

The invention also relates to a core network node comprising a packetdata gateway access supporting node handling mobile user station accessover an access network, which core network further provides access toexternal, global or local, or third party controlled packet datanetworks such as Internet or intranets etc. Still further the inventionrelates to a dual or a multimode mobile user station supporting accessusing at least two different access technologies over at least twodifferent access network types to a core network. Further yet theinvention relates to a method for providing dual or multimode mobileuser stations with access to applications over a network architecturecomprising one or more core networks to which mobile user stations canbe connected or attached over an access system using a first accesstechnology.

STATE OF THE ART

New and coming generations of communication networks will be able toprovide end users with access to applications over a plurality of, ormultiple, access types using different access technologies and/ordifferent types of user terminals. However, networks of today arecapable to provide user mobility only as long as a user is roamingwithin networks using the same access technology. 3G (3GPP, ThirdGeneration Partnership Project) systems provide user access and mobilitythrough the GMM (GPRS Mobility Management), for communication betweencore network nodes and radio network nodes, particularly RNC (RadioNetwork Control node), and GTP (GPRS Tunneling Protocol) forcommunication between core network nodes on the packet switched (PS)side, i.e. for a GPRS attached user. 3GPP furthermore has specified theI-WLAN, Integrated Wireless Local Area Network, system for integratedaccess for WLAN users to 3G services. The I-WLAN standard in e.g. 3GPPTS 23.234 v. 6.5.0, TS 29.234 v.6.3.0, specifies how the user can usehis SIM/USIM (Subscriber Identity Module/UMTS SIM) and 3G securitymechanisms to be authenticated by the 3G systems and also get access to3G services.

However, today it is not possible for multi-access capable terminals,i.e. dual mode or a multimode terminals, to roam between access systemsusing different access technologies. There is no 3GPP specificationsuggesting how handover between different access systems could be made.Today existing networks could for example provide mobility on top ofaccess networks, for example using mobile IP. Such a solution is howevera non-integrated solution associated with several drawbacks. It wouldfor example require that the user terminal supports mobile IP inaddition to existing mobility support. Two mobility solutions would thenbe stacked “vertically” and the terminal would need to maintain multiplemobility states. The consequence thereof would be that the overhead onthe radio link would increase, since both mobility solutions requiresignaling in order to be able to maintain the mobility state. Anotherdisadvantage is that the complexity on the core network side also wouldincrease since new protocols and procedures would have to be supportedin addition to already existing procedures and protocols.

It is hence, today, not possible for a user to change access systemduring an ongoing session without loosing the session, for example ifchanging from a WLAN hotspot to a 3G access on leaving the hotspot orvice versa, or if he wants to change from a WLAN or a 3G system oranother system to a fixed broadband access for example when goingindoors or vice versa, without loosing the session. Thus, there is ageneral problem that needs to be solved, since there are, today,different access technologies available which are appropriate fordifferent prevailing conditions and there are also available dual ormultimode mobile user stations, but there is not provided for apossibility to change from one access system to another, hence in anoptimal way take advantage of what actually exists on the market,without loosing ongoing sessions or access to applications etc.

SUMMARY OF THE INVENTION

What is needed is therefore a network architecture that offers andsupports multiaccess mobility. Particularly a network architecture isneeded which enables integration of multiaccess systems and which allowsfor handovers between different access systems or access systems usingdifferent access technologies while still maintaining ongoing sessions,i.e. which allows session continuity, and which allows handovers betweendifferent access system without interruption of ongoing services oraccessed applications.

Particularly a network architecture is needed which provides convergenceof fixed and wireless networks, and even more particularly a networkarchitecture is needed which supports integration of multiple accesstechnologies, 3GPP as well as non-3GPP access technologies, for exampleincluding 2G, 3G, S3G as well as fixed broadband accesses such as xDSL,public Ethernets, WLANs, WiMAX etc.

Most particularly an application independent mechanism or a networkarchitecture is needed which allows an end user to be reached and toreach services through a long term stable IP-address also when changingpoint of attachment between different access types, i.e. when changingfrom one access network technology to another, for example duringongoing sessions. Particularly packet data session continuity or IPmobility for unicast is needed when moving within and between differentaccess types. As an example an arrangement or a network architecture isneeded that allows an end user to be attached to for example a UTRANwhen going indoors and e.g. deciding to put the user equipment or userstation at a holder, for example for battery loading purposes and/or forusing a loadspeaker etc., thus for example connecting to the network viaa broadband ADSL installed, without loosing the session. Vice versa auser might also want to take his user equipment out of the stationaryholder and go outdoors without loosing the session. Other particularcases relate to leaving or entering WLAN hot spots or similar from fixedbroadband connections or 3G connections or any other connections. Agenerally applicable solution is needed. Particularly a networkarchitecture is needed which is cheap and easy to build, use andimplement for operators, application or service providers as well as forend users.

A core network node is therefore also needed through which one or moreof the above mentioned objects can be achieved. Still further a mobileuser station is needed through which one or more of the above mentionedobjects can be achieved and which can be used. Still further a method isneeded for providing support of dual or multi access between differenttypes of access networks particularly without loss of session continuityetc. and, generally, through which one or more of the above mentionedobjects can be achieved.

Therefore a network architecture as initially referred to is provided inwhich said, or at least some of said packet data gateway access supportnodes, in the following simply denoted GASNs, are adapted to be capableof assigning an IP-address to an accessing mobile user station, wherebyparticularly each of said GASNs has at least one access type dependentor specific interface to at least one type of access network. At leastsaid GASNs are adapted to support communication with each other over amobility protocol interface such that a first or new GASN receiving arequest for change of access type from a mobile user station is adaptedto establish information about which previous packet data GASN themobile user station is or was accessing over before the change, orgenerally, be able to establish mobile user station related information.Such new GASN is adapted to, using the established information about themobile user station or more particularly about the user, update anestablished communication context concerning the mobile user station forthe previous GASN or alternatively creating a new communication contextconcerning the mobile user station with the first GASN, such thatmobility between different access network types is enabled for a mobileuser station without interruption of an ongoing session.

In one implementation one or more of said GASNs is or are adapted tosupport access over more than one access network type, i.e. can handledifferent access technologies. Alternatively one or more of said GASNsis/are dedicated for access over a particular access network type. In anetwork comprising one or more core networks, there may also be GASNseither having all or one dedicated interface(s) or a dedicated interfacefor different access types in any combination. Particularly each GASN isdedicated for access over a particular access network type, or there isone, or a limited number of GASNs for each access type.

In one embodiment a previous GASN is adapted to support the access atleast over a WLAN and/or WiMAX and/or a fixed broadband access network,for example (x)DSL, and/or a public Ethernet and/or 2G or a 3G or a S3Gaccess network and said new or first GASN is adapted to support accessover at least one or more of the above mentioned access networks, atleast one being different from that/those of the previous GASN.

In one implementation a GASN may comprise a modified GGSN (Gateway GPRSsupport node) with an extended functionality or it may be particularlymodified or extended in so far that it has a particular access typedependent or specific interface and is capable to establish userinformation about previous GASN, and supports intercommunication withother GASNs as discussed above. It may also comprise a modified CGSN(Combined GPRS Support Node) providing the above mentionedfunctionalities. For example some of the SGSN (Serving GPRS SupportNode) functionality within the CGSN may be implemented in a 3G radionetwork control node RNC or similar of the access network instead.

Particularly at least one of said GASNs comprises a modified (asdiscussed above) PDG (Packet Data Gateway) supporting at least WLANand/or WiMAX access.

A GASN may also comprise a modified PDG supporting fixed broadbandaccess or even more particularly a modified BRAS (Broadband AccessServer).

Particularly a previous GASN is adapted to act as an anchor point for auser connection after handover between different access type networks,i.e. after handover to another GASN if still needed. Particularly thatanchor point handles policy and charging functionalities etc.

In one implementation the network architecture comprises at least twocore networks and multiaccess handover is supported also between corenetworks. A previous GASN may then be provided in a first core network,e.g. a home core network, for a mobile user station whereas the new GASNmay be provided in a second core network, e.g. the home core network ofthe mobile user station or vice versa. The inventive concept is alsoapplicable if a mobile user station is roaming between two visited corenetworks.

Particularly the intercommunication mobility protocol comprises GMM(GPRS Mobility Management)/GTP. Most particularly the IP-addressallocated to the user of a mobile user station is kept, i.e. notaffected, by a handover between different access systems or differenttypes of access systems.

In one implementation one of the access networks comprises a WLAN or aWiMAX or a fixed broadband access network and the respective access typedependent interface comprises an interface for setting up an IP-sectunnel between the mobile user station and a GASN, said GASN for exampleat least comprising a modified PDG/TTG (Tunnel Terminating Gateway) or aBRAS respectively over an access node of the access network, for examplea WAG (Wireless Access Gateway) or a DSLAM (DSL Access Multiplexer)respectively. Another access network may comprise for example a 3Gaccess network, for example a UTRAN with an access network dependentinterface comprising a GMM (/GTP).

As another alternative Mobile IP is used as intercommunication mobilityprotocol between GASN:s a new GASN and a previous GASN, of which onee.g. is a PDG/TTG. New MIP (Mobile Internet Protocol) Extension formatscan easily be defined to transport the required information whichcurrently are not defined for MIP, e.g. RAT (Radio Access Type), QoS(Quality of Service) negotiated (normally included in GTP) etc.

Most particularly a GASN is adapted to communicate with the HSS, forexample HLR/AAA (Authentication Authorisation Accounting) serverhandling the mobile user station requiring access mobility in order forthe new GASN to establish the previous GASN address or identity. In analternative implementation, in order to establish information about theaddress of the previous GASN, it is supposed that routing areas alsohave been specified for, for example, WLAN and/or fixed broadband accessnetworks in order to allow for a GPRS ISRAU (Inter SGSN Routing AreaUpdate) procedure to be implemented for informing a GASN about previousGASN. In still another implementation it is supposed that theinformation about previous GASN is included in a message or in theaccess request from the mobile user station when the mobile user stationrequests interaccess system handover.

In a particular implementation the network is adapted to, upon handoverfrom one access system to another for a mobile user station, create aroute between the mobile user station and the new GASN via the previousGASN, which hence forms an anchor (point) GASN. In a particularimplementation the established communication context is a PDP contextand said PDP context is updated or a new PDP context is established uponhandover from one access system to another.

In a Mobile IP implementation, instead of updating (setting up a new)PDP context, a MIP registration is requested from the previous GASN,which responds to the request. When performing a handover from e.g.UTRAN (or generally a 3G access network) to e.g. a WLAN (or fixedbroadband access network), and an IP sec tunnel is set up, preferablythis includes agreeing about a secure association before the tunnel isset up, and an IP address is given. As an example IKE exchange is used,and a tunnel is set up based on keys. Alternatively a tunnel is set upfirst, without assigning an IP address, or a temporary IP address isfirst given which is replaced by the “original” one. As long as the“same” IP address can be used, tunnel set up can be done in differentmanners.

The invention therefore also provides a core network node as initiallyreferred to which is adapted to be capable to assign an IP-address toaccessing mobile user stations. It has at least one access typedependent or specific interface at least for one type of accessnetworks. Further it has a mobility protocol interface supportingcommunication with other packet data gateway access supporting nodes andit is adapted to, for establishing information about which was theprevious GASN for a mobile user station requesting access, or even moreparticularly about the user of a mobile user station or relatedinformation. Further it is adapted to, using the establishedinformation, update an established communication context concerning themobile user station from the previous GASN or, alternatively creating anew communication context concerning the mobile user station such thatmobility between different access types, i.e. different access systemsusing different access technologies, is enabled for a mobile userstation without interruption of or affecting an on-going session orservice. Alternatively it may support sending a request for MIPregistration from a previous GASN, in case mobile IP is used.

In one implementation the GASN is adapted to support access of more thanone access type, i.e. it has at least two different access typedependent interfaces to at least two different access network types.Alternatively it has only one access type dependent or specificinterface to one specific access network type. In one implementation ithas an access type dependent interface supporting WLAN/WiMAX access.Most particularly it then comprises a modified PDG (Packet DataGateway)/TTG (Tunnel Terminating Gateway) modified such as to providethe features referred to above. Alternatively or additionally it has anaccess type dependent or access type specific access interfacesupporting fixed broadband access network access, for example xDSL. Itmay then for example comprise a modified BRAS. Still further,alternatively or additionally, it has an access type dependent interfacesupporting 3G or 2G radio network access, for example UTRAN access. Itmay then comprise a modified or extended GGSN or a modified SGSN forexample with a limited functionality compared to a conventional CGSN forexample in that some of the functionality, particularly at least part ofthe SGSN functionality of the CGSN, is moved to a radio network controlnode or similar, or a multiaccess edge node connected to a packet datanode, for example a GGSN, an SGSN or a CGSN with the conventional or amodified functionality.

Preferably the core network node is adapted to act as an anchor pointfor a mobile user station having requested handover to another accessnetwork type or if it is the home GASN requesting multi-access handoverfrom one “visited” GASN to another “visited” GASN. Most particularly themobility protocol (between GASNs) is GTP. Alternatively Mobile IP (MIP)is used. The core network node (GASN) is particularly adapted toestablish information about previous GASN through communication with themobile user station HSS, particularly HLR/AAA. Alternatively it isadapted to retrieve information from a mobile user station request (atchange of access type) concerning previous GASN. Still further, it issupposed that routing areas have been defined also for e.g. WLANs orfixed broadbands, and the GASN is adapted to use the GPRS ISRAUprocedure to establish the previous GASN.

The invention therefore also provides a dual or multimode mobile userstation supporting access using at least two different access networktypes to a core network. It comprises means for detecting loss ofconnection to an access system or for detecting an optional, availableother access system of a different type that for some reason is to bepresented as an option or considered to be better, and/or for detectingactual connection to another access system type, and means comprising analgorithm triggering transmission of an access system change request tosuch other access system type, said access request comprisinginformation about previous access network type. However, it is notnecessary that information about the previous access network type isprovided but in some cases the provided information merely relates tothere being a change of access types.

The invention also suggests a method as initially referred to, whichcomprises the steps of;

receiving an access request relating to access over a second, or new,access network in a core network node comprising a second (or new)packet data gateway access support node;

establishing information about the previous or first GASN over which themobile user station previously was provided with access to the corenetwork and/or the home GASN;

using a mobility protocol to, using said information about the previousnode, update an existing, previous communication context, alternativelysetting up a new communication context;

keeping the previous GASN or the home GASN of the mobile user station asan anchor point;

informing the mobile user station that the access is provided over saidsecond or new access network, and hence providing the mobile userstation with access over the new access network without interrupting oraffecting an ongoing session.

Particularly the involved packet data gateway access supporting nodescommunicate with mobile user stations or access nodes over respectiveaccess type dependent or access type specific interfaces. Particularlyintercommunication between GASNs using the mobility protocol comprisesusing the GPRS GTP protocol modified to support such communication.Alternatively MIP is used.

In some embodiments the establishing step comprises; sending a requestfor the address of the previous GASN to the HSS (HLR/AAA) of the mobileuser station from the second or new GASN. Alternatively the establishingstep comprises establishing, from information contained in a messagee.g. the access request message, from the mobile user station, theaddress or the identity of the previous GASN, or alternatively,supposing that routing areas are defined for all concerned accessnetworks, implementing the GPRS ISRAU procedure to establish informationabout the address or the identity of the previous GASN.

Most particularly the method comprises the step of, after completedhandover from one access system to another of another type, creating aroute where the anchor GASN, i.e. the previous GASN, or the home GASN ifthey are not the same, is the new or second GASN. Even more particularlythe method comprises the step of; keeping the same user IP addressduring handover between different access networks.

Particularly the method comprises the step of, preforming a handoverfrom a previous type of access network to a new access network of adifferent access type or implementing a different access technology,said access networks comprising two different of the WLAN, WiMAX, fixedbroadband network for example an(a) xDSL, a 2G, 3G or a S3G network or apublic Ethernet etc.

The basic concept of the present invention is to provide multiaccessthrough enhancing and reusing existing technology. For exampleGPRS-intra system mobility is provided by GMM/GTP or MIP. With theextensions that are proposed, it will be possible to use the GTP/MIPprotocol to fulfill the requirements for multi-access and mobilitybetween different access technologies. According to the invention theuser can for example roam between I-WLAN, Interworking WLAN, (fixedbroadband) and 3G systems etc. while keeping session continuity. Atleast as far as access change between a 3G and a WLAN, or vice versa, isconcerned, the concept is based on GTP and the I-WLAN 3GPP accessspecifications. Alternatively Mobile IP is used instead of GTP toprovide control signaling and tunneling of user data between networknodes. It should however be noted that in that case Mobile IP is notused as specified by IETF, i.e. as a protocol between terminals andnetwork mobility agents. Instead Mobile IP is solely used as a networkprotocol to replace GTP and it does not have to be supported by theterminals. It is also possible to use other protocols (mobilityprotocols) than GTP or MIP between the network nodes or GASN:s.Tunneling of user data will then be performed e.g. by one of theencapsulation protocols defined for MIP, e.g. IP-in-IP or GRE (GenericRouting Encapsulation). A mobile user station can re-use GMM also withother access types, e.g. WLAN and broadband.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will in the following be further described, in anon-limiting manner, and with reference to the accompanying drawings, inwhich:

FIG. 1 schematically illustrates a core network and three differentaccess networks implementing different access technologies andinterfacing access type specific GASNs according the invention,

FIG. 2A illustrates a core network and three access networks, whereinthe user is provided with public WLAN access,

FIG. 2B illustrates the handover procedure for the user in FIG. 2A whenrequesting UTRAN access instead,

FIG. 2C illustrates provisioning of UTRAN access for the user of FIGS.2A and 2B,

FIG. 3A illustrates a user accessing a (visited) core network over apublic WLAN which is not the own core network (CN) of the user and whowill request access to an UTRAN of the visited CN,

FIG. 3B illustrates the handover procedure for the user of FIG. 3A,

FIG. 3C illustrates the provisioning of the UTRAN access for the user ofFIGS. 3A, 3B,

FIG. 4 schematically illustrates a core network and access networkswherein a user accesses the core network over a fixed broadband accessnetwork,

FIG. 5 is a sequence diagram illustrating the procedure when a userchanges access from WLAN to UTRAN according to a first embodiment,

FIG. 6 is a sequence diagram illustrating the procedure when a userchanges access from WLAN to UTRAN according to a second embodiment,

FIG. 7 is a sequence diagram describing the procedure when a userchanges access type from a UTRAN to a WLAN according to a firstembodiment,

FIG. 8 is a sequence diagram describing the procedure when a userchanges access type from a UTRAN to a WLAN according to a secondembodiment,

FIG. 9 is a sequence diagram describing the procedure when changingaccess type from a UTRAN to a WLAN according to a third embodiment,

FIG. 10 is a very schematical block diagram of a GASN, and

FIG. 11 is a very schematical block diagram of a modified RNC

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one example of a network structure according to the presentinvention. It comprises here one core network 100 which comprises anumber of core network nodes, here denoted GASNs. In the embodimentshown in FIG. 1 the core network 100 comprises a first GASN₁ 10 whichhas an access dependent or access specific interface 1 ₁ to an accesssystem which here is a WLAN/WiMAX 200, particularly to a WLAN accessgateway 210 which is the access node which concerns the access network.GASN₁ 10 particularly comprises a PDG (Packet Data Gateway) modifiedaccording to the invention. It further comprises another GASN, GASN₂ 20,which has an access type dependent interface 1 ₂ to a, here, GPRS/UMTSradio access network, UTRAN 201, i.e. to an access node in the radioaccess network which particularly may be a radio network control nodeRNC-X 220 which here means a conventional RNC modified according to theinvention or modified so as to, for example, comprise some functionalitywhich normally is provided in an SGSN (Serving GPRS Support Node), or ifimplemented, part of the SGSN functionality of a CGSN (Combined GPRSSupport Node) normally including SGSN as well as GGSN functionality.GASN₂ 20 is a modified GSN (GSN-X) in that it, in addition to supportaccess specific interfaces to access networks and intercommunicationwith other GASN:s and HSS for returning previous access node addressinformation etc. as will be discussed below, also may comprise the, ormost of the, GGSN functionality, possibly some of the SGSNfunctionality, or particularly the SGSN functionality that is notprovided for in the RNC-X 220 or correspondingly the GGSN part of a CGSNfunctionality and some of the SGSN functionality of a CGSN etc. The corenetwork 100 further comprises another GASN₃ 30 which has an access typedependent interface 13 to the access node DSLAM (DSL Access Multiplexer)230 of a fixed broadband access network 202. GASN₃ 30 and DSLAM 230 mayalso be modified as discussed above or in some other appropriate manner.GASNs 10, 20, 30 e.g. provide access to external packet data networks,such as for example Internet or generally a third party controlledpacket data network.

Mobility providing interfaces are provided between the respective GASN:s10, 20, 30; here the interfaces are denoted 2 ₁, 2 ₂. Particularly saidmobility interfaces 2 ₁, 2 ₂ comprise GTP (GPRS Tunneling Protocol)interfaces, here for example between a modified PDG/TTG 10, a GSN-X 20and a modified BRAS 30 which are used for multiaccess handover. Asdiscussed earlier in this application, e.g. Mobile IP can be used as analternative to GTP to provide control signaling and tunneling of userdata between the GASNs of concern. It is here supposed that mobile userstation or user equipment 5 accesses GASN₁ 10, particularly, a PDG or aTTG, over WLAN 200 according to the 3GPP I-WLAN specification comprisingthe setting up of an IP-sec tunnel between UE 5 and GASN₁ 10. For GPRSthere may be an SGSN or not depending on which 3GPP release that isconsidered or used. The inventive concept covers both alternatives.

According to the inventive concept the end user, for example UE 5,should keep his IP-address during inter-access system handover i.e. ifthere is a handover, e.g. to UTRAN 201 or a fixed broadband 202 from theWLAN or in the other direction, i.e. for any handover between differentaccess networks. It is further supposed that the mobile user station isa dual mode or multimode user station, for example a UTRAN and WLANcapable user station. Simultaneous access is not required but it can beimplemented for “make before brake” optimized performance.

In an advantageous embodiment policy and charging is handled in theanchor GASN as will be described more thoroughly below. As can be seenin FIG. 1 the core network also comprises a HSS 15 (Home SubscriberServer) with an AAA server 16. Also a PCRF node is illustrated handlingthe policy and charging functionalities etc.; this is however merelyindicated through dashed lines since it is not of any particularrelevance for the present invention, and it can be handled in differentmanners.

The GASN with which a user is first connected, here GASN₁ 10,particularly a modified PDG/TTG, shall remain anchor point of amulti-access handover, although in roaming cases generally the anchorpoint remains in the home CN.

In this case, i.e. if the user makes a handover to UTRAN 201 or to thefixed broadband 202, there will be two GASNs involved in the paththrough the core network 100. Therefore the old or previous GASN needsto be found after the handover, i.e. in this case the old GASN would beGASN₁ 10. As will be described more thoroughly below, the old orprevious GASN can be found in different manners and the inventiveconcept is not limited to any particular way of establishing theprevious GASN, but covers any way of establishing the previous GASN, andthree examples will be given. According to a preferable implementationthe old (previous) GASN is found via HSS 15 and AAA 16 as will be morethoroughly described with reference to FIGS. 2B and 3B. In analternative implementation the previous GASN can be found supposing thatrouting areas also are specified for example for WLAN and fixedbroadband access networks, through using the GPRS ISRAU method.According to a third alternative embodiment the mobile user stationscould be provided with information about the address of the previousGASN and send this information to the new GASN at handover. This methodis however sometimes less attractive, since operators are reluctant toexpose details about their networks, for example node IP-addresses.

These methods are also covered by the inventive concept as well as otherpossible methods but the following examples will show embodimentscomprising HSS (HLR)/AAA communication.

The block diagrams in FIGS. 2A-2C describe the procedure when end userstation 5 makes a handover from WLAN access to GPRS/UTRAN access. It ishence supposed, in FIG. 2A, that end user 5 is attached to I-WLAN i.e.attached through WLAN 200 to WAG 210 as in FIG. 1 to GASN₁′ 10′ over anaccess type dependent interface 1 ₁ and an IP-sec tunnel is set-upbetween end user 5 and GASN₁′ 10′. The respective figures are similar toFIG. 1 with the difference that GASN₁′ 10′ has two dedicated or accesstype dependent interfaces, namely interface 1 ₁ to WLAN 200 andinterface 1 ₃′ to the fixed broadband 202 (operated by operator A). HereWLAN is operated by operator C and UTRAN by operator B, also responsiblefor the core network 100. In this respect FIG. 2A is similar to FIG. 1,although it does not have to be different operators, or not differentoperators as shown, and the core network does not have to have the sameoperator as UTRAN 201 etc.

FIG. 2B is similar to FIG. 2A, but it is here supposed that the user 5attached to I-WLAN 200 via an IP-sec tunnel which has authenticated andhas access to 3G services for example looses contact with the WLANsystem 200 or for some other reason decides to make a handover to 3G. Aswill be explained, a modified routing area update will take place. Inthis embodiment a case is illustrated where the involved 3G system doesnot have a SGSN, and a GASN wherein part of the SGSN functionality ismoved to RNC-X 220. A case with a legacy 3G system including a SGSNwould be similar.

Hence, it is here supposed that a routing area update request, I, issent using GMM signaling to RNC-X 220. Subsequently RNC-X 220 sends acreate PDP context request, II, over the access type dependent orspecific interface 1 ₂ to GASN₂ 20. GASN₂ 20 then needs to know theaddress of the previous GASN to which the mobile end user station 5 wasconnected and therefore sends a request to HSS/AAA 15′, 16 using aRadius or Diameter protocol, III. When the requested information hasbeen provided to GASN₂ 20, i.e. when GASN₁′ 10′ has the address of theprevious GASN, GASN₂ 20 sends a create (or, here update, PDP contextrequest), IV, to GASN₁′ 10′. The procedure will be explained more indetail below with reference to the sequence diagrams in FIG. 5 or FIG.6.

Finally a routing area update accept, V, is sent (via GASN₂ 20) fromRNC-X 220 to the mobile user station 5 (GMM signaling). In thecommunication between the GASNs, GTP or MIP may e.g. be used. Preferablyresource control functions are handled by PCRF before as well as afterthe handover. When the handover is completed, a route is created via theanchor GASN, here GASN₁′ 10′ and the new GASN, i.e. GASN₂ 20, to themobile user station 5.

FIG. 2C finally illustrates the access to UTRAN 201. Access for mobileuser station 5 user plane traffic is provided via two GASNs in the localcore network 100, namely new GASN₂ 20 and GASN₁′ 10′, forming an anchorpoint, over GTP-U as illustrated in the figure between mobile userstation 5 and RNC-X 120, and RNC-X 120 and GASN 20, as well as betweenGASN 20 and GASN 10′. Furthermore, GASN 20 may for instance comprise anextended GGSN i.e. a GGSN with an extended functionality according tothe present invention or a CGSN also extended according to the presentinvention but where some of the SGSN functionality may or may not betransferred to the possibly correspondingly modified RNC-X 220.

FIGS. 3A-3C are figures similar to FIGS. 2A-2C but instead describing anexample of a roaming case from one GASN to another GASN usinginter-access technology according to the present invention for ahandover when the anchor point is in a home core network, here CN 2(H)101′. The visited core network is here denoted CN 1 (V) 100′.

In this case of roaming access is changed from public WLAN access toUTRAN access and the access networks are both connected to the visitedcore network 100′. The inventive concept of course also applies to othercases of roaming e.g. from access over an access network of a first corenetwork to for example an access network using a different technologybut connected to another core network where both may be visited networksor either of them may be a home core network; the functioning issimilar. Generally, if a local anchor point is used in the VPLMN, thefunctioning will be similar to what will be described for example withreference to FIG. 5. If a local anchor point is not used in the VPLMN(Visited Public Land Mobile Network), the method will still be similarbut may also have some elements similar to a GPRS ISRAU. The home anchorGASN will remain while the serving GASN is switched from the previousGASN to the new GASN.

Hence, in FIG. 3A it is illustrated a visited core network 100′ and ahome core network 101′, i.e. a home core network for the mobile userstation 5 ₁. The visited core network 100′ comprises a number of GASNs,namely GASN 1 10 ₁ having an interface to WLAN 200 ₁, i.e. an accessnetwork type dependent interface 1 ₁₀, GASN 2 20 ₁ for UTRAN 201 ₁access via RNC-X 220 ₁ over the access type dependent interface 1 ₂₀,GASN 3 30 ₁ with access type dependent interface 1 ₃₀ to DSLAM 230 ₁ offixed broadband network 202 ₁. There is also a further GASN 4 40 ₁ witha Gi+interface to IP TV. It also has a type dependent interface 1 ₄₀ toDSLAM 230 ₁. GASN:s 10 ₁, 20 ₁, 30 ₁, 40 ₁ communicate with each otherover interfaces 2 ₁′, 2 ₂′, 2 ₃′, 2 ₄′, 2 ₅′ using a mobility protocolas discussed above with reference to the preceding figures (e.g. GTP orMIP). Illustrated are also HSS 15 ₁ and AAA 16 ₁. The home network CN 2101′ is here only schematically illustrated and only GASN 5 ₀ 50 ₀ isillustrated, although also this core network generally has more GASNs.Also illustrated are, as for the core network 100′, a HSS 15 ₀ and AAA16 ₀. The GASN:s 10 ₁, 20 ₁, 30 ₁, 40 ₁ are connected respectively toGASN 50 ₀ of CN 2 101′ over roaming interfaces 3 ₁, 3 ₂, 3 ₃ over whiche.g. GTP tunnels can be set up. It is also here supposed that mobileuser station 5 ₁ accesses over WLAN 201 and an IP sec-tunnel over theinterface 1 ₁₀ is set up to GASN 1 10 ₁. Provisioning of local servicesand home services respectively merely is schematically illustrated inthe figure and it is actually not a part of the present invention.

FIG. 3B is similar to FIG. 3A but it is now supposed that the mobileuser station 5 ₁ for some reason as explained wants or needs access overUTRAN 201 instead. Mobile user station 5 ₁ therefor sends a routing areaupdate request to RNC 220 ₁, I′, which thereupon sends a create PDPcontext request to GASN 2 20 ₁ over the access type specific interface 1₂₀, II′. GASN 2 20 ₁ then, as described with reference to FIG. 2B, needsto know or get information about the previous GASN address, andtherefore sends a previous GASN address request, III′, using themobility protocol, here over a roaming interface, to HSS/AAA 15 ₀, 16 ₀of the home core network 101′ which is the home network of mobile userstation 5 ₁. At reception of the needed information, GASN 2 20 ₁ sends acontext request to GASN 1 10 ₁ which was the previous GASN, IV′. Theupdate PDP context request (or create PDP context request) is sent fromGASN 20 ₁ to GASN 50 ₀, V′, and the GTP tunnel (here) is moved frombeing between the previous GASN 10 ₁ and GASN 50 ₀ to being between GASN20 ₁ and GASN 50 ₀. Finally a routing area update accept is sent fromRNC 220 ₁ to the mobile user station 5 ₁, VI′. FIG. 3C, which is similarto FIG. 3B simply illustrates the UTRAN access with the GTP (here)tunnels between the mobile user station 5 ₁ and RNC 220 ₁, between RNC220 ₁ and GASN 2 20 ₁, and GASN 2 20 ₁ and GASN 5 50 ₀ respectively, theanchor point hence being the GASN 50 ₀ of the home core network 101′.

FIG. 4 is a simplified block diagram similar for example to FIG. 1 witha core network 100″ that can be accessed by means of three differenttypes of accesses, namely over UTRAN with a number of RNCs, RNC-Xillustrated in the figure, by WLAN access where the WLANs comprisesWAG:s and over a fixed broadband with a DSLAM. The core network 100″comprises GASN 10″, for example an extended PDG, PDGX, with an accesstype specific interface 1 ₁″ to WAG of WLAN 210″, a GASN 20″ with anaccess type specific interface 1 ₂″ to RNC-X of UTRAN 220″ and a GASN30″, e.g. a modified BRAS (Broadband Remote Access Server), with anaccess type specific interface 1 ₃″ to DSLAM of a fixed broadband 230″.It is here supposed that an IP sec-tunnel is set up between the end userstation 5 ₂ and GASN₃ 30″. This figure is merely intended to show thatalso non-3GPP access technologies shall be covered. Such systems may befixed broadband access networks, for example an ADSL connection in thehome. It is here supposed that a specific GASN/BRAS in the core networkprovides of the operator access. Particularly the GASN₃ 30″ is built upon a PDG (providing WLAN access) and the same mechanisms are used as forI-WLAN, i.e. an IP Sec tunnel is set up between the mobile user station5 ₂ and GASN₃ 30″. With these assumptions, the same multi-accesshandover procedures as used for I-WLAN to UTRAN handover and asexplained above are applicable. The figure also illustrates the (GTP)tunnels set up using the mobility protocol between the different GASN:s.

FIG. 5 is a sequence diagram describing how a handover from WLAN toGPRS/UTRAN can be performed according to one embodiment of the inventionusing GTP as a mobility protocol. It is here supposed that the user isattached to I-WLAN and hence authenticated and having access to 3Gservices but for some reason needs to make a handover to 3G/UTRAN. AnRRC (Radio Resource Control) connection is or will be established. It isthen supposed that a routing area update (RAU) request is sent fromMS/UE to RNC-X, which is a modified RNC that supports the functionsaccording to present invention, 1. The RAU message may contain IMSI,Update Type, . . . to RNC-X. Update type shall e.g. somehow indicate“update from WLAN access” or similar. In this case the parameters suchas P-TMSI, VLR TMSI, P-TMSI Signature, old RA etc. may be empty.Subsequently, 2, RNC-X sends a create PDP context request to new GASN.New GASN selection could for example be policy based and provided bymeans not covered by the present invention. The MS/UE indicates thatIP-address is not requested. The routing area update request message maybe piggybacked up to the new GASN and handled therein. A routing areaupdate request may alternatively, 1′, be sent directly from MS/UE to thenew GASN in an alternative implementation.

In the next step, 3, the new GASN requests the address of the previousGASN from HSS/AAA in this implementation, and receives a response. Asdiscussed earlier in the application, the routing area update requestmay contain an identifier, for example NAI (Network Address Identifier),RAI (Routing Area Identifier) etc. of the old GASN, e.g. PDG/TTG, suchthat the new GASN can find it without having to contact the HSS/AAA.Subsequently, 4, the new GASN sends an update PDP context request (e.g.with new GASN address, QoS Negotiated, Tunnel Endpoint Identifier,serving network identity, CGI (Cell Global Identifier)/SAI (Service AreaIdentifier), RAT type) to the previous GASN. Alternatively a create PDPcontext message may be used since the old GASN did not actually have anold GTP tunnel but rather an IP-sec tunnel to the MS/UE. However, theprevious GASN remains anchor point. Previous GASN then sends an updatePDP context response, if an update PDP context request was sent, to thenew GASN, 5. Security functions may optionally be executed, 6. The newGASN informs the HSS about the change of GASN by sending an updatelocation with e.g. GASN number, GASN address, IMSI, IMEISV to the HSS,7. It should be clear that possibly not all this information is requiredand the IMEISV (International Mobile Equipment Identifier SoftwareVersion) is sent preferably only if the ADD (Automatic Device Detection)function is supported.

HSS sends Insert Subscriber Data, for example with the IMSI,subscription data, to the new GASN, 8, which validates the presence ofthe MS/UE in the (new) routing area. The new GASN constructs a MM(Mobility Management) context for the MS/UE and returns an InsertSubscriber Data Acknowledgement message (for example with IMSI) to theHSS, 9, which acknowledges the update location by sending an updatelocation acknowledgement (IMSI) to the new GASN, 10.

The new GASN then sends a create PDP context response (for example withP-TMSI, VLR TMSI, P-TMSI Signature) to RNC-X, 11. The routing areaupdate response message may be piggybacked from the GASN, i.e. the newGASN, if handled by the GASN (new), 11.

Finally the RNC-X responds (or forwards transparently if handled in thenew GASN) to the MS with a routing area update accept (e.g. with P-TMSI,VLR TMSI, P-TMSI Signature etc.), 12, and the MS/UE finally confirms thereallocation of the TMSI:s by returning a routing area update completemessage to RNC-X, 13.

In an alternative implementation, illustrated in the sequence diagram ofFIG. 6, the Mobile Internet Protocol, MIP, is used as a mobilityprotocol between GASN:s, here between new GASN and an old (previous)GASN, e.g. a PDG, between a WLAN and UTRAN. Preferably new MIP Extensionformats are defined to transport the required information that currentlyare not defined for MIP (e.g. RAT (Radio Access Type), QoS negotiated(normally included in GTP) etc.) which are needed by the GASN.

In the sequence diagram of FIG. 6, sequence or message 1 ₁ correspondsto message 1 of FIG. 5. However, then RNC-X sends a MIP registrationrequest to the new GASN, Foreign Agent FA, 2 ₁. GASN selection may bepolicy based and provided for in any appropriate manner. UE/MS indicatesthat IP address is not requested. The RAU request message may bepiggybacked up to the new GASN and handled there. Message 3 ₁corresponds to message 3 of FIG. 5, and will therefore not be furthercommented upon (previous GASN address request and response).

However, then a MIP Registration Request (new GASN address) is sent fromnew GASN to the old GASN, e.g. a PDG, 4 ₁. Alternatively a PDP contextmessage might be used since the old GASN actually did not have an oldGTP-tunnel, but rather an IP sec-tunnel to MS/UE. The old GASN remainsthe anchor point. The old GASN returns a MIP registration response (oran Update PDP context response), 5 ₁. Messages 6 ₁-13 ₁ correspond tothe messages 6-13 discussed with reference to FIG. 5.

Finally user data is tunneled between the previous GASN and the new GASNusing an encapsulation protocol defined for MIP, e.g. IP-in-IP or GRE,141.

FIG. 7 is a sequence diagram illustrating the opposite procedureaccording to a first GTP-based implementation of the present invention,i.e. here an UTRAN to I-WLAN handover, when a user decides or needs tomake a handover from a UTRAN to a WLAN access. Hence, it is heresupposed that the WLAN tunnel is set up between MS/UE and a new GASN,for example PDG-X, 0′, e.g. a temporary IP address is used as discussedearlier in the application or it is possible to do it without assigningan IP address etc. It should be enabled to keep the same IP address asused in UTRAN. The MS/UE sends a routing area update request message,for example with IMSI, Update Type etc. to the new GASN, 1′. Update typeshall for example indicate “update from UTRAN access”. In this case theparameters P-TMSI, VLR TMSI, P-TMSI Signature, old RA etc. may, but donot have to, be present. The new GASN, for example a PDG, requests theaddress of the old GASN from HSS/AAA, and receives a response.Alternatively a routing area update request may contain an identifier,for example NAI, RAI etc. of the previous GASN so that the new GASN canfind the previous GASN, without having to contact the HSS/AAA, 2′.

The new GASN, or PDG, sends an update PDP context request with e.g. newGASN address, QoS Negotiated, Tunnel Endpoint Identifier, servingnetwork identity, CGI/SAI, RAT type etc to the GASN concerned, i.e. theprevious GASN, 3′. Previous GASN then sends an update PDP contextresponse to the new GASN, for example PDG, 4′. Security functions mayoptionally be executed now, 5′, but it is merely illustrated through adotted line since this does not form part of the present invention. Thenew GASN then informs HSS about the change of location by sending anupdate location message for example with GASN number, GASN address,IMSI, IMEISV to HSS, 6′. IMEISV is particularly only sent if the ADD issupported. HSS then sends Insert Subscriber data with for example IMSI,subscription data corresponding to the new GASN, 7′. The new GASNvalidates the presence of the MS/UE. The new GASN then constructs an MMcontext for the MS/UE and returns an Insert Subscriber dataacknowledgement (IMSI) message to the HSS, 8′, and HSS acknowledges theupdate location by sending an update location acknowledgement (IMSI) tothe new GASN, 9′.

The new GASN then responds to the MS/UE with a routing area updateaccept, 10′ for example with P-TMSI, VLR TMSI, P-TMSI Signature etc.(which however do not exist on the WLAN side), 10′. Finally the MS/UEconfirms the reallocation of e.g. the TMSI:s or P-TMSI:s by returning arouting area update complete message to the new GASN, 11′. It should beclear that this merely illustrates one particular implementation of theinventive concept for a UTRAN to I-WLAN handover.

FIG. 8 is a sequence diagram illustrating a UTRAN to I-WLAN handoveraccording to another GTP-based implementation. When the terminalconnects to I-WLAN, it performs authentication using IKEv2 and then setsup an IP Sec tunnel to the new GASN, e.g. PDG/TTG. In order to updatethe PDP context in the previous GASN and to establish the IP address ofthe MS before tunnel set up is completed, it is proposed to implicitlydo a Routing Area Update during the tunnel set up procedure. This couldbe seen as piggybacking the Routing Area Update messages onto IKEv2and/or IP sec messages. There are different possibilities fortransporting the RAU information in IKEv2 messages. Options include e.g.the Vendor ID Payload of IKEv2 messages or Notify Payload. It is alsopossible to define new IKEv2 Payload types to carry RAU information.

It should be noted that the message sequence of FIG. 8 is an exampleonly. The message exchange in IKEv2 may look different (different numberof round trips etc.) depending on type of authentication, type ofcredentials etc. that are used. In the example below, the RAUinformation is included in the third, fourth and fifth IKE_AUTHmessages. However, it is also possible to transport the RAU informationin other IKE messages than the ones shown below.

IKE, Internet Key Exchange, v.2 is described in IETF Internet Draft,Draft-IETF-IP sec-IKEv2-17, dated 23.9.2004.

Below the sequence is briefly described:

-   -   1 ₁′ The MS/UE and the new GASN, e.g. a PDG, exchange the first        pair of messages of IKEv2.    -   2 ₁′ The MS/UE sends an IKE_AUTH Request message to the new        GASN, e.g. a PDG.    -   3 ₁′ The PDG communicates with the AAA server a part of the        IKEv2 authentication. Details are not shown.    -   4 ₁′ The PDG responds with IKE_AUTH Response containing the PDG        ID, EAP-Request (Extensible Authentication Protocol) etc.    -   5 ₁′ The MS sends a IKE_AUTH Request message to the new GASN        (PDG). The message contains the RAU information needed. Update        Type shall indicate “Update from UTRAN access”. In this case the        parameters P-TMSI, VLR TMSI, P-TMSI Signature, old RA etc. may        be present.    -   6 ₁′ The new GASN (PDG) communicates with the AAA server a part        of the IKEv2 authentication. Details are not shown.    -   7 ₁′ The new GASN (PDG) requests the previous GASN address from        HSS/AAA. An alternative is that the Routing Area Update request        contains an identifier (e.g. NAI, RAI, . . . , ) of the previous        GASN so that the TTG can find it without having to contact the        HSS/AAA. Another alternative is that this step is performed        simultaneously with step 5 ₁′ above.    -   8 ₁′ The new GASN (PDG) sends an Update PDP Context Request (new        GASN (PDG) Address, QoS Negotiated, Tunnel Endpoint Identifier,        serving network identity, CGI/SAI, RAT type) to the previous        GASN concerned.    -   9 ₁′ The previous GASN sends an Update PDP Context Response to        the new PDG.    -   10 ₁′ The new GASN (PDG) informs the HSS of the change of        location by sending Update Location (PDG Number, PDG Address,        IMSI, IMEISV) to the HSS. IMSEIV is sent if the ADD function is        supported.    -   11 ₁′ The HSS sends Insert Subscriber Data (IMSI, subscription        data) to the new GASN (PDG) which validates the presence of the        MS.    -   12 ₁′ The new GASN (PDG) constructs an MM context for the MS and        returns an Insert Subscriber Data Ack (IMSI) message to the HSS.    -   13 ₁′ The HSS acknowledges the Update Location by sending Update        Location Ack (IMSI) to the new GASN (PDG).    -   14 ₁′ The new GASN (PDG) responds to the MS with an IKE_AUTH        Response. The messages contains an EAP-Success which is part of        the IKEv2 authentication. The message also contains the Routing        Area Update Accept information (P-TMSI, VLR TMSI, P-TMSI        Signature).    -   15 ₁′ The MS sends a IKE_AUTH Request message to the new GASN        (PDG). The MS confirms the reallocation of the TMSI:s by        including Routing Area Update Complete information to the PDG.    -   16 ₁′ The new GASN (PDG) completes the IKEv2 procedure by        sending a IKE_AUTH Response.

A handover from UTRAN to I-WLAN can also be performed using an MIP basedmobility protocol between a new GASN (e.g. PDG) and a previous GASN. Asreferred to above new MIP Extension formats are defined to transport therequired information, e.g. RAT type etc. Such a procedure isschematically illustrated in FIG. 9. The steps are briefly discussedbelow:

-   -   1 ₂′ The MS/UE and the new GASN (PDG) exchange the first pair of        messages of IKEv2.    -   2 ₂′ The MS sends a IKE_AUTH Request message to the new PDG.    -   3 ₂′ The new GASN (PDG) communicates with the AAA server a part        of the IKEv2 authentication. Details are not shown.    -   4 ₂′ The new GASN (PDG) responds with a IKE_AUTH Response        containing the PDG ID, EAP-Request etc.    -   5 ₂′ The MS sends a IKE_AUTH Request message to the new PDG. The        message contains the RAU information needed. Update Type shall        indicate “Update from UTRAN access”. In this case the parameters        P-TMSI, VLR TMSI, P-TMSI Signature, old RA etc. may be present.    -   6 ₂′ The new PDG communicates with the AAA server a part of the        IKEv2 authentication. Details are not shown.    -   7 ₂′ The new PDG requests the previous GASN address from        HSS/AAA, cf. 7 ₁′, FIG. 8.    -   8 ₂′ The new PDG sends MIP Registration Request to the previous        GASN concerned. The MIP message contains the required        information (new PDG Address, QoS Negotiated, Tunnel Endpoint        Identifier, serving network identity, CGI/SAI, RAT type).    -   9 ₂′ The previous GASN sends to new PDG an Update PDP Context        Response.    -   10 ₂′ The new PDG informs the HSS of the change of location by        sending Update Location (PDG Number, PDG Address, IMSI, IMEISV)        to the HSS. IMEISV is sent if the ADD function is supported.    -   11 ₂′ The HSS sends Insert Subscriber Data (IMSI, subscription        data) to the new PDG. The new PDG validates the MS:s presence.    -   12 ₂′ The PDG constructs an MM context for the MS and returns an        Insert Subscriber Data Ack (IMSI) message to the HSS.    -   13 ₂′ The HSS acknowledges the Update Location by sending Update        Location Ack (IMSI) to the new PDG.    -   14 ₂′ The new PDG responds to the MS with an IKE_AUTH Response.        The message contains an EAP-Success which is part of the IKEv2        authentication. The message also contains the Routing Area        Update Accept information (P-TMSI, VLR TMSI, P-TMSI Signature).    -   15 ₂′ The MS sends an IKE_AUTH Request message to the new PDG.        The MS confirms the reallocation of the TMSI by including        Routing Area Update Complete information to the PDG.    -   16 ₂′ The PDG completes the IKEv2 procedure by sending an        IKE_AUTH Response. (Messages 9 ₂′-16 ₂′ correspond to messages 9        ₁′-16 ₁′ of FIG. 8.)

Finally FIG. 10 is a block diagram of an exemplary GASN according to oneembodiment of the present invention. This particular implementationactually shows a new node comprising a modified GGSN that may includesome or all existing GGSN functions and other new functions as well. AGASN may also be an evolved or modified node that supports other typesof access networks such as a PDG/TTG supporting I-WLAN access or anevolved BRAS that supports broadband access. Further, it may support oneor more access network specific accesses. In FIG. 7 particularly thefunctionalities illustrated within the dashed line concerning mobilityare novel and important for a handover between different access systems,particularly comprising functionality of the control layer for routingarea update, in this case, RNC-X relocation, session management andintersystem change/handover. The other functionalities are known andwill not be further described herein.

Similarly FIG. 11 is a block diagram of an example of an RNC-X that is anew node comprising an enhanced or modified RNC that may includeexisting RNC functions and other new functions as well, for example somefunctions normally included in an SGSN. FIG. 11 is included hereinmerely for explanatory reasons. The functionalities that are essentialfor the functioning according to the inventive concept are illustratedwithin the dashed lines in the box mobility of the control layer, namelypaging, idle-mode support, RNC-X relocation, mobility management andintersystem change/handover.

It is an advantage of the present invention that e.g. GTP can be reusedand evolved for multi-access mobility, among others since GTP is aworking protocol under the control of 3GPP. The mobile user terminalwill reuse existing 3GPP mobility management and session managementprocedures, and thereby save internal state and protocol handlingcompared to if additional protocols are needed for multi-access specificfeatures. The network only has to implement the GTP protocol formobility related tunneling (if a GTP implementation is used).

Another advantage is that the terminal can use a single mobilitymanagement solution (GMM). The terminals do not have to supportadditional mobility protocols such as Mobile IP in order to achievemobility in a multi-access scenario.

As an alternative, Mobile IP can be used as an intra-network protocolinstead of GTP. The network then needs to support both GTP (for GPRS)and MIP (for multi-access). In this case the main advantage is that theterminal can continue to use GMM also for multi-access since it is notaware of which is the protocol that is used inside the network. However,also other mobility protocols may be constructed.

It should be clear that the invention is not limited to the specificallyillustrated embodiments but it covers any type of handover between anytypes of access systems irrespectively of whether in visited or homenetworks etc. Also the nodes can be varied in a number of different waysas long as they support the features specified in the appended claims.

1. A network system comprising: at least one core network, wherein eachcore network comprises a number of packet data gateway access supportingnodes (GASNs), handling mobile user station access over an accessnetwork, wherein said core network further provides access to one ormore global packet data communication networks, and one or more nodesholding subscriber and/or mobile user station related information,wherein said packet data gateway access supporting nodes are adapted to:assign an IP-address to accessing mobile user stations, have at leastone access type dependent interface to at least one type of accessnetwork, support inter-communication over a mobility protocol interface,at reception of a request for change of access type from a mobile userstation, establish information about the previous packet data gatewayaccess supporting node of the mobile user station, and use theestablished information to update an established communication contextconcerning the mobile user station or create a new communication contextconcerning the mobile user station such that mobility between differentaccess network types is enabled for a mobile user station withoutinterruption of an ongoing session, and in acting as a previous GASN,act as an anchor point for the user after a handover to another accessnetwork type, the mobility protocol being used to provide controlsignaling and user data tunneling between previous and new accesssupport nodes, wherein at least one of said packet data gateway accesssupporting nodes is adapted to support access over more than one accessnetwork type, and wherein the intercommunication mobility protocol isMobile Internet Protocol (MIP).
 2. A network system according to claim1, wherein one or more or each of said packet data gateway accesssupporting nodes is/are dedicated for access over a particular accessnetwork type.
 3. A network system according to claim 1, wherein at leastone packet data gateway access supporting node, GASN, is adapted tosupport access at least over a WLAN and/or a WiMAX and/or a fixedbroadband access network, and/or a public Ethernet and/or a 2G or 3G ora S3G and wherein at least one other packet data gateway accesssupporting nodes is adapted to support access at least over a WLANand/or a WiMAX and/or a fixed broadband access network, and/or a publicEthernet and/or a 2G or a 3G or a S3G and wherein said GASNs supportaccess over different types of access networks.
 4. A network systemaccording to claim 1 wherein at least one of said GASNs comprises amodified Gateway GPRS support node (GGSN) with an extended functionalityor a modified Serving GPRS support node (SGSN), or a modified PacketData Gateway (PDG)/Tunnel Terminating Gateway (TTG) supporting at leastWLAN and/or WiMAX access or a modified PDG supporting fixed broadbandaccess.
 5. A network system according to claim 1 wherein theintercommunication mobility protocol comprises GPRS Mobility Managemnt(GMM)/GPRS Tunneling Protocol (GTP).
 6. A network system according toclaim 1 wherein an IP address allocated to a user of a mobile userstation is unaffected by handover between different access networks ortypes of access networks.
 7. A network system according to claim 1wherein an access network comprises a WLAN or a fixed broadband accessnetwork and wherein the access type dependent interface comprises aninterface for setting up an IP-sec tunnel between the mobile userstation and a GASN over an access node of the access network.
 8. Anetwork system according to claim 1, wherein a General Packet RadioService (GPRS) Inter SGSN Routing Area Update (ISRAU) procedure isadapted to be used for informing a GASN about previous GASN based onrouting areas specified for WLAN and/or fixed broadband access networks.9. A network system according to claim 1, wherein the GASNs are adaptedto establish information about previous GASN by means of informationincluded in messages from a mobile user station requesting handoverbetween different access system types.
 10. A network system according toclaim 1, wherein means are provided for, upon handover from one accesssystem to another for a mobile user station, creating a route betweenthe mobile user station, and the new GASN via the previous GASN, saidprevious GASN hence forming at least a local anchor GASN.
 11. A corenetwork node comprising: a packet data gateway access supporting nodehandling mobile user station access over an access network and providingaccess to external global or local or third party controlled packet datacommunication networks, wherein it is adapted to be capable to assign IPaddresses to accessing mobile user stations, wherein it has at least oneaccess type dependent interface to at least one type of access network,wherein it has a mobility protocol interface supporting communicationwith other packet data gateway access supporting nodes, wherein it isadapted to establish information about which was the previous packetdata gateway access supporting node for a mobile user station requestingaccess for establishing, or acquiring user or mobile user stationrelated information, and wherein it further is adapted to, using theestablished user or mobile user station related information, update anestablished communication context concerning the mobile user stationwith the previous packet data gateway access supporting node or create anew communication context concerning the mobile user station, such thatmobility between different access network types is enabled for a mobileuser station requesting change of access type without interruption of oraffecting an ongoing session or service, and wherein it is adapted toact at least as a local anchor point for a mobile user station havingrequested handover to another access network type, wherein the mobilityprotocol is used to provide control signaling and user data tunnelingbetween previous and new access support nodes, wherein the core networknode is adapted to support access over more than one access networktype, and wherein the intercommunication mobility protocol is MobileInternet Protocol (MIP).
 12. A core network node according to claim 11,wherein it has an access type dependent interface supporting WLAN/WiMAXaccess and wherein it comprises a modified Packet Data Gateway, PDG. 13.A core network node according to claim 11, wherein it has an accessinterface supporting fixed broadband access network access and whereinit comprises a modified Broadband Remote Access Server (BRAS).
 14. Acore network node according to claim 11, wherein it has an access typedependent interface supporting 3G radio access network access and/orUTRAN access, and wherein it comprises a modified/extended Gateway GPRSsupport node (GGSN) or a modified Combined GPRS Support Node (CGSN) or amulti-access edge node connected to a packet data node.
 15. A corenetwork node according to claim 11, wherein it is adapted to establishinformation about previous GASN through communication with the HomeSubscriber Server (HSS) or Home Location Register (HLR)/AuthenticationAuthorization Accounting (AAA) of the mobile user station.
 16. A corenetwork node according to claim 11, wherein it is adapted to retrieveinformation from the mobile user station request concerning previousGASN or that it is adapted to use General Packet Radio Service (GPRS)Inter SGSN Routing Area Update (ISRAU) to establish the previous GASN,wherein routing areas are defined for WLAN and for fixed broadband. 17.A method for handling dual or multimode mobile user station access to acore network system comprising one or more core networks, said mobileuser station having accessed the one or more core networks over anaccess network using a first access technology, wherein the methodcomprises the steps of: receiving an access request relating to accessover a second or new access network in a second or new packet datagateway access supporting node, GASN, during an ongoing session,establishing, in the second or new packet data gateway access supportingnode, information about the previous or first GASN over which the mobileuser station previously was provided with access and allocated an IPaddress, using a mobility protocol or, using said information about theprevious GASN, providing communication between said previous GASN and/ora home GASN of the mobile user station to update an existing, previouscommunication context, or set up a new communication context, keepingthe previous GASN at least as a local anchor point, informing the mobileuser station that access is provided over said second or new accessnetwork, and providing the mobile user station with access over the new,second, access network without interrupting or affecting the ongoingsession, and keeping the same, allocated IP address, and using themobility protocol to provide control signaling and tunneling of userdata between the previous and new packet data gateway access supportnodes, wherein at least one of said packet data gateway accesssupporting nodes is adapted to support access over more than one accessnetwork type, and wherein the intercommunication mobility protocol isMobile Internet Protocol (MIP).
 18. A method according to claim 17,wherein packet data gateway access supporting nodes intercommunicateusing the mobility protocol, said mobility protocol comprising theGeneral Packet Radio Service (GPRS) Tunneling Protocol (GTP) or theMobile Internet Protocol (MIP).
 19. A method according to claim 17,wherein the establishing step comprises: sending a request for theaddress of the previous GASN to a node holding subscriber or mobile userstation related information from the second or new GASN, or establishingfrom information contained in a message from the mobile user station,the address or identity of the previous GASN or, implementing theGeneral Packet Radio Service (GPRS) Inter SGSN Routing Area Update(ISRAU) procedure to establish information about the address or identityof the previous GASN, routing areas being defined for all concernedaccess networks.